class A {
   double f(double x,double y) {
     return x+y;
   }
}
class B extends A {
   double f(int x, int y) {
     return x*y; 
   }
}
public class E {
public static void main(String args[]) {
     B b=new B();
     System.out.println(b.f(3,5));     //代码1
     System.out.println(b.f(3.0,5.0)); //代码2
   }
}
